<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
        "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <title>ID选择器</title>
    <style type="text/css">
        #bold{
          font-weight:bold;  /*粗体*/
         }
        #green{
           font-size:20px;
           color:#009900;
          }
    </style>
</head>
<body>
   <p id="bold">ID选择器1</p>
   <p id="green">ID选择器2</p>
   <p id="green">ID选择器3</p>
   <p id="blod green">ID选择器4</p>

</body>
</html>